Protein Deficit Research Articles

BONE MINERALIZATION OF SCHOOL AGE CHILDREN ACCORDING TO CALCIUM INTAKE

Nutrition is one of the factors that influences bone mineralization (BM). We have shown that the Chilean teenager has a low calcium intake during a period of rapid calcium accretion, which may favor osteoporosis in adult life. Thus, we evaluated the influence of a low calcium intake on BM in school age children. We studied 36 children with calcium intakes below the recommended allowance (RDA) and 28 controls of the same age and sex with an adequate calcium intake. Calcium intake was measured by three 24 hour recollection surveys, the percentage of adequation of weight for height (W/H) according to WHO tables, and puberal development was assessed by the method of Tanner. Bone mineral density (BMD) and total bone mass (TBM) were determined in whde body, spine and hip, with a Norland densitometer (Gd 156). The group with calcium intake below 50% had a lower % of adequation of height for age (97.7 ± 4.0%), TBM (98.9 ± 17.9) and BMD (97.8 ± 11.1%) in whole body compared with the group with intake over 100% (115.9 ± 17.4; 109.7 ± 18.0 and 104.7 ± 11.1%, respectively). In spine and hip there was a clear tendency for a lower TBM and BMD, which did not reach statistical significance. The recollection survey showed a lower protein intake in the group with low calcium intake compared with controls. The influence of isolated calcium deficit or in combination with protein deficit upon skeletal mineralization is discussed.

Effects of long-term protein excess or deficiency on whole-body protein turnover in sheep nourished by intragastric infusion of nutrients

The effect of long-term dietary protein excess and deficit on whole-body protein-N turnover (WBPNT) was examined in lambs nourished by intragastric infusions of nutrients. Ten sheep were given 500 mg N/kg metabolic weight (W0.75) per d from casein for 2 weeks and then either 50 (L), 500 (M) or 1500 (H) mg N/kgW0.75 per d for 6 weeks. Volatile fatty acids were infused at 500 kJ/kgW0.75 per d. Daily WBPNT was measured by continuous intravenous infusion of [1-13C]leucine 3 d before, and on days 2, 21 and 42 after the alteration in protein intake. Whole-body protein-N synthesis (WBPNS) was calculated as the difference between WBPNT and the protein-N losses as urinary NH3 and urea. Whole-body protein-N degradation (WBPND) was then estimated from WBPNS minus protein gain determined from N balance. Fractional rates of WBPNS and WBPND were calculated against fleece-free body N content. WBPNS rates at the L, M and H intakes were respectively 35.1, 41.5 and 63.7 g/d (P < 0.001) on average over the 6 weeks and WBPND rates were 39.5, 41.1 and 56.8 g/d (P < 0.001). The fractional rates of WBPNS were 5.01, 6.37 and 7.73% per d (P < 0.001) while those of WBPND were 5.64, 6.29 and 6.81% per d (P < 0.005) respectively. On days 2, 21 and 42, WBPNS rates at intake H were 54.0, 61.8 and 75.4 g/d (P = 0.03) respectively, and WBPND rates were 43.2, 56.4 and 70.9 g/d (P = 0.03); at intake L the amounts were 38.2, 34.2 and 32.8 g/d for WBPNS (P = 0.003) and for WBPND were 43.4, 38.0 and 36.9 g/d (P = 0.016) respectively. There were no significant (P > 0.05) differences in fractional rates of WBPNS and WBPND with time at either the L or H intake. We concluded that absolute protein turnover was affected both by dietary protein intake and body condition while the fractional rate of turnover was predominantly influenced by intake.

Insertion of a transpyloric feeding tube during laparotomy in the critically injured: rationale and plea for routine use

Although clinical and experimental evidence favours early enteral feeding in the critically injured, provision of such enteral feeds can be difficult. Gastric feeds are often not tolerated and may lead to aspiration. An intolerance of gastric feeds leads to a cumulative energy and protein deficit and may result in the initiation of expensive parenteral nutrition (TPN). An alternative and under-utilized technique to ensure enteral access in trauma victims is the insertion of a transpyloric (nasojejunal) feeding tube during emergent laparotomy. We have employed this method of enteral access with success. In the following report, we describe this technique, provide an illustrative case with a cost comparison between nasojejunal feeds and TPN, present the rationale for such a mode of enteral access and outline the indications and contraindications. Enteral access by the intra-operative insertion of a transpyloric feeding tube allows immediate/early enteral feeding that is easy, safe, reliable and inexpensive.

Factors limiting the erythropoietin response in rapidly growing infants with congenital nephrosis on a peritoneal dialysis regimen after nephrectomy

To prevent anemia in seven small children with congenital nephrotic syndrome of the Finnish type (age range 1 to 4 years), we gave recombinant human erythropoietin in a dose up to 150 IU/kg/per week. We then studied the limiting factors during 14 weeks. On a peritoneal dialysis regimen after nephrectomy, the patients grew considerably (range +0.1 to 2.2 kg/14 wk; mean + 1.3 kg/14 wk). The amount of blood taken for laboratory studies was estimated. Although the estimated erythrocyte volume increased, the improvement was masked in most patients by enhanced growth. In two patients the target hemoglobin value of 10 gm/dl was reached, and in three patients transfusions were avoided. The reticulocyte count rose in dose-dependent fashion. In five patients protein malnutrition was not prevented, although intake of protein was as recommended. The gradual decrease in serum ferritin values indicated that mobilization of iron stores was adequate. Serum iron values decreased, although in general remaining within normal limits. In six patients the serum copper concentration was low and in two the serum aluminum concentration was slightly elevated. Two patients had several episodes of infection. We conclude that in rapidly growing infants and small children receiving peritoneal dialysis after nephrectomy, the maintenance or elevation of the hemoglobin concentration depends on several limiting and coinciding factors. We speculate that, when protein is limited, body growth has priority over erythropoiesis. A higher dose of erythropoietin might have evoked a better response in hemoglobin concentration but might also have resulted in progression of the protein deficit.

Complement facilitates macrophage phagocytosis of inhaled iron particles but has little effect in mediating silica-induced lung inflammatory and clearance responses

Complement-mediated mechanisms are known to play a role in pulmonary inflammation and clearance responses to some types of inhaled particles. The present studies were undertaken to investigate the role of complement in mediating pulmonary inflammation and/or phagocytosis as a function of particle clearance in rats exposed to silica or carbonyl iron (CI) particles. Both particle types were shown to be weak activators of serum complement in vitro. In these studies, normal and complement-depressed (CVF-treated) rats were exposed to aerosols of CI or silica particles for 6 hr at 100 mg/m3. Following exposure, alveolar fluids and cells from sham and dust-exposed animals were recovered by bronchoalveolar lavage (BAL) at several time periods postexposure and measured for a variety of biochemical and cellular indices. In addition, pulmonary macrophages were cultured and studied for morphology and phagocytosis. Our results showed that CI exposure did not produce cellular or biochemical indices of pulmonary inflammation, either in normal or complement-depleted rats. However, fewer phagocytic macrophages were recovered from the lungs of CVF-treated, CI-exposed rats than from normal exposed animals. In contrast, silica inhalation produced a sustained PMN inflammatory response in the lungs of exposed rats, measured up through 1 month postexposure, along with significant increases in BAL fluid levels of LDH, protein, and alkaline phosphatase (P less than 0.05) and deficits in pulmonary macrophage phagocytic functions. Cobra venom factor (CVF) treatment prior to exposure in rats had no significant effect upon the silica-induced parameters, suggesting that complement may not play an important role in the acute pulmonary response to silica. The results indicate that complement may play a role in mediating CI-related macrophage clearance responses but has little effect upon sustained silica-induced pulmonary inflammatory parameters.

The effects of food protein content on the performance of pigs previously given foods with low or moderate protein contents

ABSTRACTAn experiment was conducted to study the ability of the pig to recover from the effects of a period on a food deficient in crude protein (CP). Forty young pigs were given free and continuous access to foods with either 150 (L) or 252 (M) g CP per kg in period 1 of the experiment, from 6·3 kg to 13·4 and 12·3 kg live weight respectively. These live weights were expected to give equal lipid-free empty body weights. In period 2, four males and four females from each of the period 1 treatments were given access to either M or a food with 377 g CP per kg (H) to a live weight of 30 kg, when the 32 pigs were killed.Pigs on L took 11 (s.e. 0·6) days longer to complete period 1, and had, at the end of this period, 0·20 (s.e. 0·03) kg less protein and 1·20 (s.e. 0·06) kg more lipid in their bodies than the M pigs, at a common ash weight. In period 2, pigs from L grew at a faster rate (750v.633 (s.e.d. 20) g/day), ate food at the same rate (1115v.1085 (s.e.d. 35) g/day) and converted food more efficiently (0·676v.0·585 (s.e.d. 0·016) g gain per g food) than those from M. At 30·3 kg live weight the pigs from L had corrected their protein deficit relative to ash and reduced their fatness, so that they had the same protein: ash ratio and only 0·47 (s.e. 0·12) kg more lipid in their bodies than those from M. This was the result of a higher rate of gain of protein and water, a lower rate of lipid gain and similar rate of ash gain by the pigs from L than those from M. In the first 7 days of period 2 the pigs from L gained weight at 1·4 times the rate of those from M. In the final 7 days there was no significant effect of period 1 treatment on growth rate. The pigs from L given food H in period 2 were more efficient than those given M in period 2 (food conversion efficiency (FCE) values of 0·884 and 0·791 respectively; s.e.d. 0·027), but this difference was reversed in the final 7 days (FCE values of 0·521 and 0·603 respectively). t I is concluded from these results that a period of eating a food of low protein content produces a reduced protein: ash and an increased lipid: ash ratio in the body and reduced growth rate and efficiency. When subsequently pigs are given a food of sufficiently high protein content, the protein: ash and lipid: ash ratios return to normal. The repletion of labile protein reserves, with their associated water, leads to a substantial increase in the rate of live-weight gain. The lower lipid content of the gain leads to a high efficiency. The duration of these effects depends on the protein content of the food given.

Plasma albumin repletion after transfusion with polymerized hemoglobin

Pyridoxalated polymerized hemoglobin (PPHG) has promise as a blood substitute for transfusing patients with hemorrhage. Exchange transfusion with PPHG depletes plasma proteins. The purpose of this study was to determine if, during the early repletion of intravascular proteins, albumin was transported from the interstitium of skin or skeletal muscle into the vascular compartment. PPHG was prepared from stroma-free human hemoglobin (100–120 mg/ml). The Hct of anesthetized rats dropped from 42 ± 4% to 10 ± 1% after exchange transfusion. Immediately postexchange plasma albumin declined from 24 ± 2 to 6 ± 3 mg/ml. Five hours postexchange transfusion plasma albumin had doubled and the skin and skeletal muscle albumin content was 80% of control. These data indicate that a shift of interstitial albumin from skin and skeletal muscle can rapidly replace plasma protein deficits after massive transfusion with PPHG.

Effects of the β2-adrenoceptor agonist, clenbuterol, on muscle atrophy due to food deprivation in the rat

The effects of a β 2-adrenoceptor agonist, clenbuterol, on body weight and protein metabolism of gastrocnemius muscle, heart, and liver were studied in rats subjected to 50% food restriction or fasting. Food restriction by 50% for 7 days caused a complete cessation of growth and reductions in the mass, protein, and RNA content of muscle, heart, and liver. The ratio of RNA to protein content was also suppressed in muscle and heart, but not in liver. Fasting for 3 days caused loss of body weight (BW), reductions in the mass, protein, and RNA content, and the ratio of RNA to protein of gastrcnemius muscle, heart, and liver. Oral administration of clenbuterol (∼0.6 mg/kg BW/d) to food-restricted animals did not affect BW, but did increase in the mass, protein, and RNA content, and the ratio of RNA to protein of gastrocnemius muscle. The protein content of heart was also increased. Twice-daily injections of clenbuterol (2 mg/kg body weight/d) to fasting animals had no effect on BW or the mass or protein content of gastrocnemius muscle or liver, but both parameters were stimulated in heart. The results indicate that the anabolic action of clenbuterol are maintained when substrate availability is reduced by food restriction, but this effect is lost during severe protein and energy deficit (fasting).

12 Genetically engineered and affinity purified plasma proteins

Blood transfusion to correct a plasma protein deficit began as long ago as 1840 with a report of the infusion of whole, fresh, uncrossmatched blood to a haemophilic boy (Lane, 1840) which stopped him from bleeding to death. Doubtless due to problems of incompatibility, this was not seriously followed up until the late 1920s (Payne and Steen, 1929), when it was reported that intravenous infusion of citrated human plasma, which had been stored frozen for 5 days, corrected the clotting time and caused bleeding to cease in a haemophilic boy. Large scale plasma separation to derive therapeutic infusable protein fractions was developed during World War II by Cohn and colleagues (1946). The Cohn fractions included a fibrinogen concentrate (fraction I), albumin (fraction V), immunoglobulins (fraction II) and aand [3-globulins (fractions IV and III). There were, however, no specific coagulation factor fractions; this is not surprising since at the time of development (1940-1945) no assays were available for coagulation factors other than fibrinogen and prothrombin. Minot and Taylor (1947) showed that Cohn's fraction I also contained what they called antihaemophilic globulin (i.e. it shortened the clotting time of haemophilic blood) but that its potency was highly variable. This study antedated the discovery that haemophilia was of two types, A and B, due to factor VIII and IX deficiencies respectively. In the 1950s, MacFarlane and co-workers (1954) developed some concentrates of factor VIII (measured using a specific assay) from bovine and porcine blood. Although highly valuable as the first true factor VIII concentrates, these preparations were limited in clinical use by severe side-effects due to animal proteins eliciting allergy and the aggregatory effect of animal von Willebrand factor (vWF) on human platelets. Various concentrates of factor VIII were produced during the 1950s and early 1960s but the first to gain wide popularity because of its simplicity and reliability was Judith Pool's cryoprecipitate (Pool et al, 1965). During the 1960s and 1970s further steps were introduced into factor VIII purification relying largely on the differential precipitation according to molecular weight.

Nutritional Status, Growth and Development in Children Undergoing Intensive Treatment for Cystic Fibrosis

Dietary intakes were measured over a period of 5 days in 36 malnourished and 36 well-nourished patients with cystic fibrosis. Both energy and protein intakes were significantly less in the malnourished patients for the two age groups studied: 4-9.99 years (p less than 0.01 for both parameters), and 10-16 years (p less than 0.05 and p less than 0.01, respectively). In both age groups and both patient groups, average protein intakes were well in excess of the recommended daily intake, but energy intake in the malnourished patients was below the recommended daily intake. Nutritional supplementation of 10 malnourished patients with a polymeric formula, infused overnight via a gastrostomy tube, resulted in a seven-fold increase in weight gain (p less than 0.001) and a doubling of linear growth velocity (p less than 0.01) over a period of 18 months, compared to the 18 months prior to gastrostomy feeding. Measurements of total body nitrogen in eight of these patients demonstrated a 38% increase in body nitrogen content over 12 months, indicating a replenishment of the protein deficit.

Nutritional status and morbidity on an irrigation project in Turkana District, Kenya.

The research reported on here was undertaken to identify the most important contributors to continuing high mortality on a small-scale irrigation project at Nakwamoru in Turkana District, Kenya. The health status of project settlers had not been assessed prior to the present study, which was undertaken in 1978-79, a decade after the project was started. The purpose of the study was to estimate the nutritional status of project children and the major causes of morbidity in the Nakwamoru area. Nutritional status was derived from cross-sectional anthropometric measurements, including weights, heights, triceps skinfolds, and upper arm circumferences, taken on approximately 60% of project children (n = 236) aged 1-10 years. The major causes of morbidity in project settlers of all ages for the period 1973-78 were estimated from outpatient records from the local primary care facility. Age/sex patterns of clinic use were obtained through interviews. Stunting was found to be prevalent, especially in children aged 1-4, while wasting was only observed in a small proportion of the sample, indicating a seasonal pattern of malnutrition. Derived cross-sectional areas of upper arm muscle and fat were found to be low by comparison with U.S. standards, suggesting both energy and protein deficits in project children. Malaria and acute respiratory infections were found to be the major causes of illness in the local population, and both are likely to have contributed to the generally poor nutritional status of project children. Despite free biomedical care, 15% of the local population in general and 23% of adult females had never used clinic services.

Somatomedin C in dairy cows related to energy and protein supply and to milk production

ABSTRACTSomatomedin C and other hormones, as well as blood metabolites, were measured during the dry period and during lactation in dairy cows, given different amounts of energy and protein, to study metabolic and endocrine adaptations. Somatomedin C, specifically measured by radioimmunoassay after separation from its binding protein, did not exhibit typical diurnal variations, in contrast to somatotropin and insulin, which increased particularly after concentrate intake. Somatomedin C markedly decreased at parturition and reached lowest values around the peak of lactation, while levels of somatotropin, nonesterified fatty acids and ketone bodies were high and those of glucose, insulin, thyroxine and triiodothyronine were low. Thereafter somatomedin C values slowly increased up to the 12th week of lactation and remained elevated. Low energy and protein balances were characterized by particularly low somatomedin C concentrations. An additional protein deficit at peak lactation, when cows were already provided with low amounts of energy, did not further decrease somatomedin C levels. However, when high amounts of energy were given in the form of starch or crystalline fat, somatomedin C increased. Overall, there was a positive correlation of somatomedin C primarily with energy, but also with protein balances and a negative correlation with milk yield. Conversely, somatotropin increased markedly after parturition and was positively correlated with milk production and negatively with protein and energy balances. Thus, somatomedin C levels were paradoxically low in the presence of high circulating somatotropin. Insulin most closely paralleled somatomedin C levels. Therefore the anabolic state of metabolism at the end of pregnancy was characterized by high somatomedin C and insulin and relatively low somatotropin, whereas the catabolic state of early lactation was characterized by high somatotropin, low somatomedin C, insulin and thyroid hormones.

Effects of diet composition on food intake and carcass composition in rats

Since most of the weight-reduced obese humans are in a protein deficit state, this study was designed to examine whether a high protein diet (HP) enhances the restoration of lean body mass and facilitates the maintenance of weight loss. Obesity in rats was produced by 16 weeks of high fat diet (HF) feeding. In the 17th week, all HF-fed obese rats were fed a limited amount of control diet to normalize their body weights, but they still had more body fat content. The HF-fed rats were then divided into subgroups with different diets offered for 5 weeks: HP, HF or chow diet. A control group was fed the chow diet throughout the study. HP feeding maintained normal body weight and carcass composition in weight-reduced obese rats by reducing feeding efficiency levels to within normal ranges. Weight-reduced rats fed a chow diet, however, had more fat mass than controls and HF feeding stimulated weight gain again. Therefore, a HP diet has a higher probability of enhancing weight loss maintenance in weight-reduced obese subjects than does a usual well-balanced diet.

Effects of medium glutamine, glutamate, and ammonia on glutamine synthetase activity in cultured mouse astroglial cells.

Mouse astroglial cells were grown during the last week of culture in either glutamine-free or glutamine-containing medium. The addition of cortisol to the glutamine-containing medium resulted in a doubling of astroglial glutamine synthetase (GS) activity. Withdrawal of glutamine from the medium resulted in a 50% elevation of GS and addition of cortisol to such a medium resulted in a further increase in GS which was not additive to glutamine withdrawal. Both in glutamine-free and glutamine-containing medium, the addition of glutamate resulted in a depression of both basal and cortisol induced GS activity. The simultaneous addition of ammonia plus glutamate to the culture medium ameliorated the glutamate mediated depressive effects on cortisol induced but not basal GS activity. Glutamine withdrawal from the culture medium resulted in an astroglial protein deficit. The addition of ammonia to the medium considerably reduced this deficit and the addition of glutamate completely eliminated this protein deficit.

Control of protein intake in golden hamsters

Experiments were performed to investigate the behavioural responses of golden hamsters to manipulations of dietary protein availability. In the first experiment, hamsters were maintained on a protein-free diet and a powdered diet containing 64.8% protein (P64.8). When the P64.8 diet was progressively diluted with cornstarch, hamsters increased their intake of this diet fraction, but protein intake nevertheless declined. When the protein content of the diet was 16.2%, animals derived only 6% of total calories from protein and lost weight despite normal intake of calories. In the remaining experiments, hamsters were maintained on a self-selection regimen of high-protein chow, pure carbohydrate (sugar cubes), and pure fat (vegetable shortening). When high-protein chow was removed for either 5 or 10 days, total caloric intake and body weight declined, and hamsters selectively increased protein intake for several days after high-protein chow was returned. Hamsters allowed access to high-protein chow for only one hour each day markedly increased the amount of high-protein chow they ate during this hour as protein-restriction continued, but still consumed only about 10% of their normal daily protein intake on this schedule and lost 20% of starting body weight in two weeks; when free access to high-protein chow was restored, these animals selectively increased their protein intake above pre-restriction levels. Hamsters given access to high-protein chow only on alternate days demonstrated a relatively modest and slowly developing increase in protein intake, perhaps because they incurred only a moderate protein deficit. The results suggest that when protein intake falls below normal minimum requirements, hamsters will demonstrate an adaptive protein hunger but make only a limited adjustment to the dilution of a protein-containing diet fraction.

The Influence of Glucocorticoid Dose on Protein Catabolism After Renal Transplantation

Protein catabolic rate (PCR) and protein balance were measured daily by computerized mass balance studies in 20 subjects during hospitalization after renal transplantation. All hospital courses were uncomplicated. Ten subjects received approximately 1 mg/kg/day prednisone, and ten subjects received 3-5 mg/kg/day prednisone on day 1 with a tapering dose to approximately 1 mg/kg/day by discharge. In both groups, PCR rose during the first 3-4 postoperative days then stabilized at an accelerated level. PCR was significantly greater in the higher prednisone group. Despite encouragement most subjects ate less protein than prescribed, and most were in negative protein balance. Mean daily and net protein deficits were more severe in the higher prednisone group. Higher protein intakes improved protein balance. The protein catabolic effects of the two regimens have been defined and a dose dependency demonstrated. In any therapeutic situation the use of the minimum effective dose of steroids seem advised, and high protein intake should be encouraged to improve protein balance. Some steroid morbidity might thus be avoided.

Relations entre les sécrétions mammaires et les teneurs en nutriments énergétiques et azotés sanguins chez la chèvre au début de la lactation

An experiment was performed on 29 dairy goats at the onset of lactation; energy and protein deficits were maximal during the first week of lactation. This was confirmed for energy by the plasma contents on non-esterified fatty acids (NEFA), beta-OH-butyrate and glucose. However, protein deficit was more critical during the second week, as shown by plasma urea, glycine and 3-CH3-histidine contents. At that time, nutritional status depended more on udder production than on intake level. Moreover, the nutritional parameters of body lipid and protein mobilization were positively correlated. Milk protein content was positively correlated with the nutritive balance and status of the goats.

Variability in body protein loss during protracted, severe caloric restriction: role of triiodothyronine and other possible determinants

Six morbidly obese subjects were maintained in a metabolic ward for 64 days on liquid diets providing 600 to 800 kcal/day. Three received protein at a level of 1.5 g/kg desirable weight per day. The other three were given an identical diet in which half the protein was replaced by carbohydrate. Because there were no significant differences in either mean protein or mean fat losses between the two groups, the data on all six subjects were combined. Over the 64 days, the mean weight loss (±SEM) of the subjects per 1000 kcal deficit was 174.3 ± 25.5 g. The composition of this weight loss was 36.0% water, 58.9% fat, and 5.1% protein. Although the rate of fat loss was relatively constant throughout the study, wide interindividual variations in cumulative protein (nitrogen) deficit were observed. Total nitrogen losses per subject ranged from 90.5 to 278.7 g. Cumulative nitrogen loss during the first 16 days tended to correlate negatively with initial mean fat cell size and positively with initial lean body mass. Most notable was the strong negative correlation between the size of the decrease in serum triiodothyronine over the 64-day study and the magnitude of the concurrent cumulative N deficit. During severe caloric restriction, one's ability to decrease circulating serum triiodothyronine levels may be critical to achievement of an adaptational decrease in body protein loss.

Mechanisms for redistribution of plasma protein following acute protein depletion.

Acute plasma protein depletion is followed by a rapid and substantial replenishment of the protein deficit. We studied the effects of plasmapheresis on flow and composition of peripheral lymph in 11 unanesthetized sheep. Whole blood was replaced with red blood cells and lactated Ringer solution to reduce plasma protein concentration ([P]) 26-54%. At 24 h after plasmapheresis, [P] had returned halfway to base line. Lymph flow (L) increased immediately after plasma protein reduction, was maximal 3 h later, and remained elevated for more than 3 days. The increase in L was coupled with a decrease more than 3 days. The increase in L was coupled with a decrease in lymph-to-plasma protein concentration ratio ([L/P]). The plasma-to-lymph oncotic gradient was reestablished by 24 h due to the reduction in lymph protein and the partial return of [P]. After 24 h, L remained elevated despite base-line levels for all measured vascular pressures and plasma-to-lymph oncotic gradients. Although lymph flow was increased, the permeability-surface area product for protein was decreased below base line. The data confirm that the partial return of [P] in the first day after plasmapheresis is due largely to a shift of extravascular protein mass into the vascular compartment and show that redistribution is initiated by increased lymphatic return and maintained by a sustained increase in L and a decrease in protein permeability of the plasma-lymph barrier.

Transport proteins as indices of protein status

The terms protein status and protein deficiency have been used to denote several quite different concepts. Before beginning to consider how best to measure protein status, and the place of transport protein concentration in this measurement, we must be precise about what we are trying to measure. Laboratory animal investigators clearly refer to the condition resulting from an insufficiency of protein in the diet when they use these terms, irrespective of the clinical or biochemical findings that these diets produce. Clinicians on the other hand refer to a variety of clinical or biochemical findings in the patient, irrespective of the antecedent diet. Thus protein deficiency has been used synonymously with kwashiorkor, nutritional edema, and also for reduced levels of the transport proteins-albumin, transferrin (1), retinolbinding protein, and prealbumin (2). Field workers use the terms in a totally different way-to indicate a lack of body protein in the body compositional sense. It is clear that the very concept of protein deficiency enshrines a whole chain of events. Any particular investigator tacitly assumes the whole chain to exist if he observes a single link in the chain. In essence the thesis is that a protein-deficient diet leads to a loss of body protein, the loss being identified as due to protein deficiency, and not energy deficiency or some other condition, though a coincident reduction in the circulating transport proteins. This in turn leads to edema, skin sores, fatty liver, and the other features of “pure” kwashiorkor. Developing a body protein deficit is synonymous with being in negative nitrogen balance. Consideration of the numerous causes of a negative nitrogen balance indicates the totally nonspecific nature of a protein deficit with respect to various dietary components, trauma and disease. There is no constant relationship between any transport protein and the total amount of protein in the body relative to an appropriate standard; it is only when a body protein deficit arising from a specific cause is considered that a relationship is to be expected. Transport proteins have assumed a special place in the chain of events because they are thought to identify whether a body protein deficit is due to a dietary protein deficiency or not. Because of this the level of circulating transport protein, traditionally albumin, has been used to define protein deficiency in clinical practice; indeed many people hold the view that the degree of hypoalbuminaemia indicates the relative importance of a dietary protein deficiency with respect to energy, or other deficiency, in a malnourished individual. Because of the relatively long half-life of albumin, other transport proteins that respond more rapidly to alterations in the diet have been suggested as more sensitive indices of the degree of dietary protein deficiency (1, 2). For those who define protein status on the basis of the levels of these transport proteins an appraisal of their use in the evaluation of protein status is impossible: this immediately leads to a circular and self-fulfilling argument. Without an independent and true estimate it is not possible to evaluate the reliability with which any particular measurement reflects protein status. The independent measurement of protein status has to be an accurate measurement of protein intake, relative to an estimate of protein requirement, that has itself been derived without recourse to transport protein measurement. In order for a transport protein measurement to be a useful measurement of protein status it is not sufficient for it to respond precisely when a protein-deficient diet is